Crane,especially bridge crane



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CRANE, ESPECIALLY BRIDGE CRANE- Filed Sept. 30, 1968 s In ..//w m mm @www 0 H bm /.7W 2 w we n/w. l ,we @Ac/S I m59 im m mdM H d H r e @$6.0 Mfr/0 .c V ,w y 1 M 1H!! IW s stroke bompreson il ,fw bam 3,532,226 CRANE, ESPECIALLY BRIDGE CRANE Gert Bechtlotf, Madras, India, and Manfred Schmidt and Henricus Tromp, Wilhelmshaven, Germany, assgnors to Fried Krupp Gesellschaft mit beschrankter Haftung, Essen, Germany Continuation-impart of application Ser. No. 507,141, Nov. 10, 1965. This application Sept. 30, 1968, Ser. No. 763,739 Claims priority, application Germany, Nov. 11, 1964, 1,700,118 Int. Cl. B66c 17/00 US. Cl. 212-10 2 Claims ABSTRACT 0F THE DISCLOSURE A traveling crane, especially bridge crane having a transverse girder member mounted on wheels at each end to move longitudinally along rails transverse to said girder member which latter has a carriage supported thereon for movement along the girder member between its ends and which includes a resilient buffer element having means for mounting on one of the girder or abutment members positioned to limit the movement of the girder member along the rails in one direction, the resistance to compression to said buffer element increasing with the speed of compression so that if one end of said girder member has greater momentum than the other due to proximity of said carriage to said one end, movement of said girder member will be resisted by a greater compressive force at said one end than at the other end, and the girder member will be maintained substantially parallel to its rest position.

The present application is a continuation-impart application to our copending application Ser. No. 507,141, led Nov. 10, 1965, now abandoned, and relates to a traveling crane in which the crane comprises a transverse girder member mounted on wheels at each end to move longitudinally along rails transverse to said girder member which ha-s a carriage supported thereon for movement along said girder member between its ends, Iwhile abutment means limit the movement of said girder in opposite directions.

With a crane of this type it frequently happens that the carriage is at one end of the girder adjacent one of the rails. Consequently, at the limit of the travel of the girder in one direction, the end of the girder with the carriage and load exerts a far greater force on the limiting abutment means than the opposite end which has only a small force exerted by the end of the girder. When springs or similar buffer devices are used to arrest the movement of the girder, the heavy end `with the carriage will compress the buffer at that end through a much greater distance than the other end so that the girder tends to-twist or skew on the rails, and the wheels and rails are subject to` this shock.

It is, therefore, an object of this invention to provide a traveling crane of the above mentioned general character which will overcome the above mentioned drawback.

It is another object of this invention to provide a crane of the general character set forth above, which will considerably reduce the stresses on the tread wheels and the track for the crane when the latter abuts abutment means limiting its movement.

These and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawing, in which:

FIG. l illustrates a crane bridge provided with buffers of the heertofore known type and shows the inclined position of the bridge when the buffers engage other buffers or abutments.

3,532,226 Patented Oct. 6, 1970 FIG. 2 shows partly in section and partly in view a butler according to the present invention.

FIG. 3 illustrates the characteristics of a material as used, for instance, for a buffer according to the invention.

FIG. 4 -shows a crane bridge 'with buffers according to the present invention.

FIG. 5 represents a graph illustrating the course of the power force plotted over the stroke which the crane bridge performs in conformity with the compression of the buffer material after abutting against counter butfers, while employing buffers of the heretofore known type.

It has been found according to the present invention that when the abutment means limiting the girder travel are made as buffers constructed of foamed synthetic material which comprises numerous cells enclosing gas, the initial force resisting compression is very high, and the heavy loaded end of the girder will not compress the buffer as rapidly, so that the girder will not be twisted or skewed on the rails.

For the sake of completeness it may be mentioned that cushioning elements formed of foamed synthetic ma* teral have become known, buit such cushoning elements relate to car buifer and vehicle tires, none of which has the same problem as encountered in traveling cranes and outlined above. Even in vehicle buffers there is not the excessive difference in force exerted on buffers on opposite sides as is the case in a crane girder carrying a carriage with a load at one end.

Referring now to the drawing in detail, FIG. 1 illustrates the prior art and shows the top view of a crane bridge with buffer-s of a heretofore known type.

The crane carriage 1 is at the right-hand end of the crane bridge 2 so designed that the right-hand bridge end absorbs 'the greater portion of the inertia forces to be braked by the buffers than the left-hand bridge end. Inasmuch as at the same abutting speed at the buffers, in the just described circumstances, the right-hand bridge end will remain in movement longer than the left-hand bridge end, it will be appreciated that the crane buffer 3 and the counter buffer 4 will have to absorb a considerably greater amount of work than the crane buffer 5 and counter buffer 6 so that the buffers 3 and 4 'will be compressed to a greater extent than the buffers 5 and 6. This makes itself felt in the crane bridge assuming a slanted position with the result that the tread wheels or the horizontal guiding wheels and the crane track will be subjected to harmful stresses and may even bring about the danger of `a derailment. A considerable slanting of the bridge may be expected particularly when said bridge repeatedly has its buffers abut the counter buffers because the crane motor remained engaged.

These drawbacks will be avoided according to the present invention by the combination of a crane of the type involved with buffers one of which is shown partially in section and partially in view in FIG. 2. In conformity with the invention, the cylindrical buffer body 7 consists of a material which has such a characteristic that the buffer force, when the material is being compressed, will .increase with the speed at which the compression takes place. As will be seen from FIG. 2, buffer body 7 has its outer end face and its circumference covered by a plastic skin 8 for protection against sparks. Furthermore, buffer body 7 is provided with a flange 9 which serves for connecting the buffer to the buffer carrier, namely the crane bridge. Buffer body 7 as illustrated in FIG. 2 has two annular grooves 10 in order to prevent any material detachment of skin 8 from the remainder of the buffer body when the latter is compressed.

FIG. 3 shows by way of a graph. the characteristics of a material as it may be used, for instance, for a buffer according to the present invention. Plotted on the abscissa is the percent-wise compression e of the buffer, while over the ordinate there is plotted the compression stress a. The graph shows the characteristic of a material with the speed v at which the compression is effected and, more specifically, at the speed 1, 2 and 3 meters per second. It will be seen from FIG. 3 that for each value of the specific compression e the compression stress r will be the higher the greater the speed v of the compression. When the crane carriage on the crane bridge girder occupies a position to the left or the right of its central position, and when due to the different inertia forces on the two bridge ends, the buffers will be compressed to a different extent at the two bridge ends and at the same abutting speed, the characteristic of the buffer material employed in conformity with the present invention will bring about that the tendency of the bridge girder to assume a slanted position will be considerably counteracted. The ideal situation is shown in FIG. 4 in which the bridge girder 2 remains parallel to its original position.

For purposes of explaining the result obtained by the present invention, reference may be had to FIGS. 5 and 6. These figures have plotted over the ordinate the buffer force and over the abscissa the stroke of the two ends of the crane bridge in conformity with the compression of the buffer material after the buffers of the crane bridge abut against the counter buifers. More specifically, FIG. 5 shows this situation when employing buffers or buffer springs as heretofore known, whereas FIG. 6 shows the same situation when employing buffers in conformity with the present invention.

In connection with FIGS. 5 and 6, it is assumed that the crane carriage occupies a noncentral position on the bridge and that at one bridge end the mass M1 to be f braked is considerably less than the mass M2 to be braked at the other end. For instance, at a crane speed of 3 meters per second at one bridge end, a work of 7 meter tons has to be absorbed, whereas at the other bridge end a work of 12 meter tons has to be absorbed. According to FIG. 5, for both buffers at both bridge ends there prevails the same spring characteristic so that the buffer force increases proportionally to the compression of the springs. Consequently, the bridge end adjacent to the carriage will, due to the greater mass M2 and the correspondingly greater work absorption, move over a considerably longer path s2 than the path s1 over which the other buffer mass M1 moves. The difference between the two paths s2 and s1 results in a slanted position of the crane bridge as shown in FIG. l.

With the crane and butfer design according to the present invention, that bridge end which is adjacent the crane carriage will initially move over a longer path than the path over which the other bridge end moves in the same time. However, due to the correspondingly higher speed of the compression of the buffer material at the bridge end which moves over the longer path, a steeper and higher spring curve k2 applies than is the case for the other bridge end for which the spring curve k1 is characteristic. Consequently, that bridge end with the greater mass M2 will, during the further compression of the buifer material, encounter a correspondingly higher resistance than the resistance encountered by the other bridge end with the smaller mass M1. Consequently, the difference between the paths s2 and s1 over which the two bridge ends move following the abutment of their respective buffers and counter buffers is considerably less than is the case when employing heretofore known buffers, so that a harmful slanting of the bridge will be avoided. Experience has shown that the present invention has proved particularly advantageous in connection with traveling cranes, gantry cranes and loading bridges.

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawing but also comprises any modications within the scope of the invention.

Furthermore, the present invention is not limited to a Specific material. The buier material preferably consists of a porous material with gaseous enclosures in the pores, e.g., foarned synthetic rubber.

Preferably, a foamed synthetic material with gaseous enclosures is employed, e.g., elastomers or polyurethanes. The gas bubbles are uniformly distributed across the volume of the body; they may have diameters of 0.5 to 10 millimeters.

What we claim is:

1. In a traveling crane, in which the crane comprises a transverse girder member mounted on wheels at each end to move longitudinally along rails transverse to said girder member, said girder member having a carriage supported thereon for movement along said girder member between its ends, and in which an abutment member is positioned to limit movement of said girder member along said rails in one direction by buffer elements interposed between said girder member and abutment member at opposite ends to arrest movement of said girder member and carriage, a resilient buffer element having means for mounting on one of said girder or abutment members to oppose movement of said girder member, the resistance to compression of said buffer element increasing with dependence upon the time duration and the speed of compression, so that if one end of said girder member has greater momentum than the other due to proximity of said carriage to said one end, movement of said girder member will be resisted by a greater compressive force at said one end than at the other end, and the girder member will be maintained substantially parallel to its rest position.

2. In a traveling crane, a buffer as claimed in claim 1 in which said butter element is formed of foamed synthetic material having speed-dependent compression characteristics in closed cell formation and having gas bubbles enclosed in cells distributed substantially uniformly throughout said material.

References Cited UNITED STATES PATENTS 2,829,915 4/1958 Claveau 293-71 3,022,810 2/1962 Lambe 152-157 3,179,397 4/1965 Cleereman 267-1 3,294,254 12/1966 De Ment 213-221 FOREIGN PATENTS 1,115,423 10/1961 Germany.

HARVEY C. HORNSBY, Primary Examiner U.S. Cl. X.R. 

